The present invention relates generally to barcode scanners, and, more specifically, to a stationary barcode scanner.
Barcode scanners are commonly found in retail establishments such as supermarkets which require relatively high speed scanning effectiveness in view of the large number of products which are typically being purchased. In this application, either horizontal or vertical, or both, pass-by barcode scanners may be used for increasing the likelihood and speed of scanning a barcode laterally swiped horizontally across the window thereof.
In department stores, counter space is limited, and the scanner is typically located where pass-by scanning cannot be used. Instead, a presentation scanner is used which permits barcodes to be presented to the scanner with a motion that is parallel to the window normal, i.e., perpendicular to the window.
A typical barcode is printed on a label and includes a series of alternating dark bars and white spaces therebetween of varying width in a one-dimensional array in accordance with the Universal Product Code (UPC) for example. The series of bars are vertically straight and stacked horizontally parallel to each other in the form of a picket fence, and are therefore typically referred to as a picket barcode.
In order to read the barcode, the scanner produces one or more scan lines which must traverse the bars and spaces of the barcode in sequence for correspondingly absorbing and reflecting light therefrom. The reflected light is therefore modulated by the barcode and follows a reverse path into the scanner and is detected by a photodetector and decoded in an electrical processor for determining the information encoded in the barcode, typically used for identifying the attached product and its price.
In this way, a barcode may be quickly read and decoded provided, however, that one or more scan lines properly traverse the barcode. Since the barcode is attached at different locations on different products and may be presented to the scanner in different orientations, a single scan line may not properly traverse the entire barcode resulting in a reading failure.
For this reason, various types of barcode scanners have been developed including handheld and stationary vertical or horizontal scanners or the combination thereof for improving the likelihood of properly reading and decoding a barcode presented in any orientation. The different types of scanners enjoy different benefits, with associated disadvantages including complexity, size, and cost.
The typical stationary scanner is relatively complex, large, and expensive since it includes a rotating spinner having mirror facets which reflect a laser beam along an arcuate path over several pattern mirrors to produce a pattern of differently directed scan lines through a window over which the barcode may be swiped or presented. The scan line pattern is controlled by relative orientation of the individual pattern mirrors and the spinner facets, and is repeated once per revolution of the spinner.
Each spinner facet is typically disposed at a different inclination angle so generally parallel sets of scan lines may be produced from a common set of pattern mirrors cooperating with the spinner. The proper selection and orientation of spinner facets and pattern mirrors is critical for effecting a corresponding scan pattern for reading barcodes. However, many compromises are typically made in configuring the scanner in view of the complexity thereof, and therefore different scanners have different capabilities and disadvantages.
For example, scanners are typically limited in their ability to read the various orientations of the barcode being scanned. The basic one-dimensional barcode is a picket barcode as described above. As such, it requires at least a single scan line to horizontally traverse in sequence each of the vertical bars thereon in order to obtain a complete scan thereof. However, if the picket barcode is rotated 90xc2x0 from its horizontal orientation to a vertical orientation it then becomes the commonly known ladder barcode with the bars extending horizontally and being stacked vertically. In this orientation, a horizontal scan line cannot read the barcode, but a vertically directed scan line is required for vertically traversing in turn the bars for reading the barcode.
The barcode may also have inclined orientations between the picket and ladder orientations including, for example, diagonal orientations 45xc2x0 counterclockwise from the vertical or 45xc2x0 clockwise from the vertical. These diagonal barcodes require different scan lines in order to properly traverse the inclined bars over the full length of the barcode to perfect a scan.
Since the complexity of the scanner increases as the number of scan lines increases and their orientation in space differs, there is a practical limit requiring compromise in each type of barcode scanner. Different scanners have different capability for reading the four basic barcode orientations, and the scanner design is rendered even more complex depending upon the intended direction of barcode swiping or presentation. In a pass-by scanner, a barcode is typically swiped in a horizontal plane, and the scan pattern is specifically configured to maximize the likelihood of an effective scan thereof. Correspondingly, the pass-by pattern has coverage gaps and lacks effective scanning capability for presentation scanning.
A presentation scanner typically has a small pattern at its window which expands outwardly therefrom, and is thusly lacks effective scanning capability for pass-by scanning.
Accordingly, it is desired to provide a barcode scanner having improved flexibility in effecting scan line patterns with reduced coverage gaps therein.
A spinner for a barcode scanner includes a plurality of mirror facets arranged oppositely in pairs in a polygon, with adjoining facets having different angles of inclination and different lengths for reflecting a laser beam in correspondingly different, variable sweep arcs. The spinner cooperates with a plurality of pattern mirrors in a barcode scanner embodiment for effecting a scan line pattern with extended coverage.